Lithium containing solid electrochemical cells

ABSTRACT

This invention is directed to lithium and lithium alloy metal substrates, coated with a polymeric layer containing dispersed lithium or lithium alloy metal particles. The coated metal finds use as anode material in solid electrochemical cells.

This application is a divisional of application Ser. No. 08/077,489,filed Jun. 14, 1993, now U.S. Pat. No. 5,366,829.

BACKGROUND OF THE INVENTION Field of the Invention

This invention is directed to a stable, more useful form of lithium,lithium alloys and substrates coated with lithium, particularly suitedfor use as anodes in secondary electrochemical cells. This inventionalso relates to high energy density electrochemical cells. A lithiumanode in such a cell is highly desirable because the use of a lithiumanode results in useful voltage at a very low equivalent weight. Theanode is the electrode which undergoes oxidation during the dischargeportion of the discharge-charge cycle.

Lithium, however, tends to react with the organic electrolyte in thecell. When this happens, the reacted lithium is lost for recyclingpurposes thereby reducing the efficiency of the cell. Such loss can leadto premature destruction of the cell. The reaction products of thelithium and the organic electrolyte are deposited on the anode,eventually effectively insulating the anode from participation in theelectrochemical reactions of the cell, thereby leading to cell failure.

Furthermore, lithium tends to form dendrites during recharge. Thesedendrites, which are nodular, poorly adhering forms of lithium, tend tofall from the anode and become isolated from the electrochemicalreactions of the cell, a process known as "lithium isolation".Additionally, the dendrites may eventually lead to short circuiting ofthe cell if bridging by the lithium from the anode to the cathode takesplace.

This invention is directed to enhancing a surface of lithium metal bycreating a conducting layer of polymeric design. The enhanced lithiumsurface finds use in the fabrication of improved electrochemical cellsand batteries made from lithium electrodes.

BACKGROUND OF THE INVENTION

Electrochemical cells containing an anode, a cathode and a solid,solvent-containing electrolyte are known in the art and are usuallyreferred to as "solid batteries". The use of certain of these solidbatteries over repeated charge/discharge cycles is substantiallyimpaired if the battery exhibits a drop in charge and discharge capacityover repeated cycles as compared to its initial charge and dischargecapacity.

Specifically, solid batteries employ a solid electrolyte interposedbetween a cathode and an anode. The solid electrolyte contains either aninorganic or an organic matrix as well as a suitable inorganic ion salt.The inorganic matrix may be non-polymeric [e.g, β-alumina, silicondioxide lithium iodide, etc.] or polymeric [e.g., inorganic(polyphosphazene) polymers] whereas the organic matrix is typicallypolymeric. Suitable organic polymeric matrices are well known in the artand are typically organic polymers obtained by polymerization of asuitable organic monomer as described, for example, in U.S. Pat. No.4,908,283. Suitable organic monomers include, by way of example,polyethylene oxide, polypropylene oxide, polyethylenimine,polyepichlorohydrin, polyethylene succinate, and an acryloyl-derivatizedpolyalkylene oxide containing an acryloyl group of the formula CH₂═CR'C(O)O-- where R' is hydrogen or lower alkyl of from 1-6 carbonatoms.

Because of their expense and difficulty in forming into a variety ofshapes, inorganic non-polymeric matrices are generally not preferred andthe art typically employs a solid electrolyte containing a polymericmatrix. Nevertheless, electrochemical cells containing a solidelectrolyte a polymeric matrix may suffer from low ion conductivity and,accordingly, in order to maximize the conductivity of these materials,the matrix is generally constructed into a very thin film, i.e., on theorder of about 25 to about 250 μm. As is apparent, the reduced thicknessof the film reduces the total amount of internal resistance within theelectrolyte thereby minimizing losses in conductivity due to internalresistance.

The solid electrolytes also contain a solvent (plasticizer) which istypically added to the matrix in order to enhance the solubility of theinorganic ion salt in the solid electrolyte and thereby increase theconductivity of the electrochemical cell.

To make a solid electrolyte, a monomer or partial polymer of thepolymeric matrix to be formed is combined with appropriate amounts ofthe inorganic ion salt and the solvent. This mixture is then placed onthe surface of a suitable substrate (e.g., the surface of the cathode)and the monomer is polymerized or cured (or the partial polymer is thenfurther polymerized or cured) by conventional techniques (heat,ultraviolet radiation, electron beams, etc.) so as to form the solid,solvent-containing electrolyte.

When the solid electrolyte is formed on a cathodic surface, an anodicmaterial can then be laminated onto the solid electrolyte to form asolid electrochemical cell.

Notwithstanding the above, the initial capacity of solid batteries isoften less than desirable. Moreover, even when the initial capacity ofthe solid battery is relatively high, such solid batteries often exhibitrapid decline in capacity over their cycle life.

Specifically, the cumulative capacity of a solid battery is thesummation of the capacity of a solid battery over each cycle (charge anddischarge) in a specified cycle life. Solid batteries having a highinitial capacity but which rapidly lose capacity over the cycle lifewill have low cumulative capacity which interferes with theeffectiveness of these batteries for repeated use.

The normal passivation layer of lithium surfaces in contact with thedescribed electrolytes are relatively brittle and unstable. When thebattery is cycled, the lithium is stripped from the anode on thedischarge half-cycle and is plated on the recharge half-cycle. The weakpassivation layer is disrupted by the cyclic process and the lithiummetal reacts further with the electrolyte. Consequently, the lithium isstripped and plated selectively over the anode surface, causing thegrowth of dendrites or nodules which can eventually short the cellthrough the electrolyte.

U.S. Pat. Nos. 5,147,739 and 5,110,696 suggest the use of compositeanodes comprising lithium or lithium alloy substrate in combination withone or more lithium insertion compounds. The intercalation compound maybe adhered, mixed, embedded, or otherwise contacted as a finelydispersed layer, coating, laminate, or mixture with the lithiumsubstrate. Such anodes, like the use of lithium/carbon anodes (U.S. Pat.No. 5,028,500), and the use of lithium alloys, although less reactivetowards the electrolyte, provide lower energy density.

It would be advantageous if the lithium surface could be enhanced by astrong and stable layer which is ionically and electronicallyconducting.

In view of the above, the art is searching for methods to enhance thecumulative capacity of such solid batteries. It goes without saying thatincreases in the cumulative capacity of solid batteries would greatlyfacilitate their widespread commercial use.

SUMMARY OF THE INVENTION

In the present invention, to promote uniform lithium plating andstripping, lithium or lithium alloy particles are dispersed in a polymerprecursor composition. The polymer precursor composition is then coatedonto a lithium or lithium alloy metal surface and polymerized thereon toform an electronically conducting layer on the metal surface.Alternatively, the particles may be dispersed in a polymer solution, orpolymer melt, which is layered onto the metal surface.

The invention encompasses a lithium or lithium alloy metal suitable foruse as an anode in an electrochemical cell wherein a surface of themetal is coated with a conducting polymer composition containingdispersed lithium or lithium alloy metal particles. Whereas the purelithium metal anode itself has been found to exhibit nonoptimal platingand stripping properties when used in a rechargeable or secondaryelectrochemical cell, according to this invention, it is found that acoating of metallic lithium or lithium alloy particles dispersed in apolymer matrix provides a vast improvement. Adverse reactions betweenthe electrolyte and the highly reactive lithium surfaces are minimized.Such a composite anode prevents dendrite growth during charging as wellreducing lithium isolation.

Examples of lithium alloys finding use within the scope of thisinvention as either metal for use as an anode, or as dispersedparticles, or both, include lithium-aluminum, lithium-mercury,lithium-zinc, lithium-magnesium, combinations thereof and other suchless reactive lithium-containing alloys. Lithium-aluminum is the mostpreferred lithium alloy for this purpose, for reasons including those ofweight and energy density.

Polymers used in the conducting polymer coating of the metal fall intotwo general classes. A first class of polymers is not electronicallyconducting, but is rendered conducting by the dispersion of lithium orlithium alloy metal particles therein. A second class of polymers isinherently conducting, particularly when doped. The first class ofpolymers are exemplified by those polymerized from radiationpolymerizable compounds which are low molecular weight ethylenicallyunsaturated compounds, preferably compounds having at least oneheteroatom in the molecule, and preferably those having at least twoterminal polymerizable ethylenically unsaturated moieties. Whenpolymerized, these compounds may form an ionically conductive polymermatrix. Then, when lithium or lithium alloy metal particles aredispersed therein, the polymers are rendered electronically conductive.

The second class of polymers are electronically conducting by nature oftheir conjugated network of double bonds, such as polypyrrol,polyacetylene, polyaniline, polyazine, poly(paraphenylene),poly(thiophene), poly(phenylene vinylene) and the like.

The polymeric coating of the metal is preferably an ultrathin layer nomore than about 50 microns in thickness, preferably from about 2 to 40microns in thickness, and most preferably from about 5 to 25 microns inthickness.

The dispersed lithium or lithium alloy metal particles are normally inthe range or from about 0.1 microns to 10 microns in diameter.Preferably in the range of from 0.2 microns to 5 microns in diameter,and most preferably in the range of from about 0.5 to 4 microns indiameter.

The lithium or lithium alloy metal particles make up more than oneweight percent of the polymeric layer, depending on the nature of thealloy. It being desirable to obtain a uniform dispersion of lithium overthe surface of the metal in the polymer layer, preferably the lithium orlithium alloy metal particles make up from about 5 to 75 weight percent,more preferably 10 to 50 weight percent, still more preferably 15 to 45weight percent and most preferably about 20 to 40 weight percent of thepolymeric layer.

In another aspect, the invention encompasses a solid electrochemicalcell including, an anode containing lithium, a cathode containing acompatible cathodic material, a solid ionically conducting electrolyteinterposed between said anode and said cathode, and a solidelectronically conducting polymeric layer comprising dispersed lithiumor lithium alloy particles interposed between said electrolyte and saidanode.

The solid electrolyte in the electrochemical cell is preferably composedof a polymer, an inorganic salt, and a solvent.

In yet another aspect, the invention is a method of making a solidelectrochemical cell the steps of which include, coating an ionicallyconducting electrolyte composition comprising radiation polymerizablepolymer precursors onto a compatible cathodic layer, partially ortotally curing the electrolyte by exposure to radiation, coating alithium or lithium alloy metal, or a lithium coated foil metal surfacewith a prepolymer composition comprising dispersed particles of lithiumor lithium alloy metal in a radiation polymerizable-polymer precursor,partially or totally curing the prepolymer composition to form a totallyor partially cured polymer layer on the metal, and placing the totallyor partially cured polymer layer on said metal in operational contactwith the electrolyte.

In one manifestation of the invention, a prepolymeric material for usein coating the surface of lithium and lithium alloy metals containscomonomers and monomers selected from radiation polymerizablepolyethylenically unsaturated compounds, wherein dispersed in saidmonomers and comonomoers are lithium or lithium alloy metal particles offrom about 0.2 to about 4 microns in diameter.

In yet another manifestation, the invention is a battery comprising aplurality of electrochemical cells which include an anode containinglithium, a cathode containing a compatible cathodic material, a solidionically conducting electrolyte interposed between the anode and thecathode, and a solid electronically conducting polymeric layercontaining dispersed lithium or lithium alloy particles interposedbetween the electrolyte and the anode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As noted above, this invention is directed to a lithium, or lithiumalloy, metal coated with a conducting polymer composition comprisingdispersed lithium, or lithium alloy particles. The metal providesenhanced capacity when used in a solid battery. However, prior todescribing this invention is further detail, the following terms willfirst be defined.

Definitions

As used herein, the following terms have the following meanings.

The term "solid polymeric matrix" refers to an electrolyte compatiblematerial formed by polymerizing an inorganic or organic monomer (orpartial polymers thereof) and which, when used in combination with theother components of the electrolyte, renders the electrolyte solid. Thesolid matrix may or may not be ion-conducting. Preferably, however, thesolid matrix is capable of ionically conducting inorganic cations (e.g.,alkali ions) .

Suitable solid polymeric matrices are well known in the art and includesolid matrices formed from inorganic polymers, organic polymers or amixture of polymers with inorganic non-polymeric materials.

Preferably, the solid polymeric matrix is an organic matrix derived froma solid matrix forming monomer and from partial polymers of a solidmatrix forming monomer.

Alternatively, the solid polymeric matrix can be used in combinationwith a non-polymeric inorganic matrix. See, for example, U.S. Pat. No.4,990,413 which is incorporated herein by reference in its entirety.Suitable non-polymeric inorganic materials for use in conjunction withthe solid polymeric matrix include, by way of example, β-alumina,silicon dioxide, lithium iodide, and the like. Suitable inorganicmonomers are also disclosed in U.S. Pat. Nos. 4,247,499; 4,388,385;4,414,607; 4,394,280; 4,432,891; 4,539,276; and 4,557,985 each of whichis incorporated herein by reference.

The term "a solid matrix forming monomer" refers to inorganic or organicmaterials which in monomeric form can be polymerized, preferably in thepresence of an inorganic ion salt and a solvent to form solid matriceswhich are suitable for use as solid electrolytes in electrolytic cells.Suitable solid matrix forming monomers are well known in the art and theparticular monomer employed is not critical. Preferably, the solidmatrix forming monomers have at least one hetero atom capable of formingdonor acceptor bonds with inorganic cations (e.g., alkali ions). Whenpolymerized, these compounds form an ionically conductive matrix.

Examples of suitable organic solid matrix forming monomers include, byway of example, propylene oxide, ethylenimine, ethylene oxide,epichlorohydrin, acryloyl-derivatized polyalkylene oxides (as disclosedin U.S. Pat. No. 4,908,283), vinyl sulfonate polyalkylene oxides (asdisclosed in U.S. Pat. No. 5,262,253 which patent is incorporated hereinby reference in its entirety), and the like as well as mixtures thereof.

Examples of suitable inorganic solid matrix forming monomers include, byway of example, phosphazenes and siloxanes. Phosphazene monomers and theresulting polyphosphazene solid matrix are disclosed by Abraham et at.,Proc. Int. Power Sources Symp., 34th, pp. 81-83 (1990) and by Abraham etal., J. Electrochemical Society, Vol. 138, No. 4, pp. 921-927 (1991) .

The term "a partial polymer of a solid matrix forming monomer" refers tosolid matrix forming monomers which have been partially polymerized toform reactive oligomers. Partial polymerization may be conducted for thepurpose of enhancing the viscosity of the monomer, decreasing thevolatility of the monomer, and the like. Partial polymerization isgenerally permitted so long as the resulting partial polymer can befurther polymerized, preferably in the presence of an inorganic ion saltand a solvent to form solid polymeric matrices which are suitable foruse as solid electrolytes in electrolytic cells.

The term "cured" or "cured product" refers to the treatment of the solidmatrix forming monomer or partial polymer thereof under polymerizationconditions (including cross-linking) so as to form a solid polymericmatrix. Suitable polymerization conditions are well known in the art andinclude by way of example, heating the monomer, irradiating the monomerwith UV light, electron beams, etc. The resulting cured productpreferably contains repeating units containing at least one hetero atomsuch as oxygen or nitrogen which is capable of forming donor acceptorbonds with inorganic cations (alkali ions). Examples of suitable curedproducts suitable for use in this invention are set forth in U.S. Pat.Nos. 4,830,939 and 4,990,413 which are incorporated herein by referencein their entirety.

The solid matrix forming monomer or partial polymer can be cured orfurther cured prior to or after addition of the inorganic ion salt andthe solvent. For example, a composition comprising requisite amounts ofthe solid matrix forming monomer, inorganic ion salt and solvent can beapplied to a substrate and then cured. Alternatively, the solid matrixforming monomer can be first cured and then dissolved into a suitablevolatile solvent. Requisite amounts of the inorganic ion salt andsolvent can then be added. The mixture is then placed on a substrate andremoval of the volatile solvent results in formation of a solidelectrolyte. In either case, the resulting solid electrolyte is ahomogeneous, single phase product which is maintained upon curing, anddoes not readily separate upon cooling to temperatures below roomtemperature. Accordingly, the solid electrolyte of this invention doesnot include a separator as is typical of liquid electrolytes.

The term "inorganic ion salt" refers to any inorganic salt which issuitable for use in a solid electrolyte. The particular inorganic ionsalt employed is not critical and examples of suitable inorganic ionsalts include, by way of example, LiClO₄, LiI, LiSCN, LiBF₄, LiAsF₆,LiCF₃ SO₃, LIPF₆, NaI, and NaSCN. The inorganic ion salt preferablycontains at least one atom selected from the group consisting of Li andNa.

The term "electrolytic cell" refers to a composite containing an anode,a cathode and an ion-conducting electrolyte interposed therebetween.

The anode is composed of a compatible anodic material which is anymaterial which functions as an anode in a solid electrolytic cell. Suchcompatible anodic materials are well known in the art and include, byway of example, lithium, lithium alloys, such as alloys of lithium withaluminum, mercury, zinc, and the like.

In the present invention, the anode is a composite of lithium or lithiumalloy metal and an electronically conducting polymer layer. The polymerlayer is also ionically conducting. By providing an anode composed of anelectronically conducting, active, polymeric layer, the cell life isvastly improved and rechargeability of the cell is enhanced. Theelectronically conducting layer performs the function of electrontransfer, and because it contains dispersed lithium or lithium alloymetal particles, it also performs at least part of the function ofproviding the electron-transfer half-cell reaction. The lithium orlithium alloy metal anode substrate to the polymer layer also functions,as usual, in the half-cell reaction. It is believed that the dispersedlithium provides a uniform distribution of active sites for thedeposition and dissolution of lithium during recharge and dischargecycles. Lithium alloy metals are preferred as the dispersed phaseprincipally for reasons of safety and efficient dispersion.

Electrically conductive polymer layers, in order to be useful in thisinvention, should have a stable electrical conductivity of at leastabout 10⁻⁶ (OHM-CM)⁻¹. The conductive polymeric layer will have aconductivity dependant on the use to which the cell is put. Underconditions requiring a high current drain, a more electrically polymerlayer will be used.

The conductive polymeric layer covers the entire active surface of theanode. The concentration of lithium or lithium alloy metal dispersed inthe polymer layer is in the range of from about 5 to 75 weight percentbased on the total weight of the polymeric layer.

When the metal powder and the polymer precursors are mixed together, theparticle size of the powder should be in the range of from sub-microndiameter to a few microns in diameter, preferably in the range of fromabout 0.2 micron to about 4 microns in diameter. Intimate mixing and theuniform distribution of the metal powder in the polymer precursors, orpolymer, is accomplished by means known in the art.

Typical lithium alloys finding use within the scope of the inventioninclude binary and other alloys of lithium with aluminum, mercury, zincand magnesium. The lithium-aluminum alloy is preferred.

The polymeric layer, in a preferred embodiment, is an organic polymerionically conducting polymeric matrix formed from monomers containingheteroatoms capable of forming donor/acceptor bonds with alkali metalcations. Such monomers or prepolymerization oligomers are exemplified bypolyethylenically unsaturated monomeric or oligomeric materials havingat least one and more preferably a plurality of heteroatoms(particularly oxygen and/or nitrogen atoms) capable of formingdonor/acceptor bonds with alkali metal cations, which are terminated byradiation polymerizable moieties. These compounds yield a conductive,supportive, solid matrix. More specifically, they are exemplified by theoligomers disclosed in U.S. Pat. No. 4,830,939, the disclosure of whichis incorporated herein by reference in its entirety.

A particularly useful group of radiation polymerizable compounds isobtained by reacting a polyethylene glycol with acrylic or methacrylicacid. Also useful in the present invention are radiation curablematerials such as acrylated epoxides, polyester acrylates, acrylatedfunctionalized polyurethane, copolymers of glycidyl ethers andacrylates, and vinyl compounds such as N-vinyl pyrrolidone. For example,halogen monomers such as vinyl chloride are preferably avoided.

Preferably, the radiation polymerizable polyethylenically unsaturatedcompounds have molecular weights of from about 200 to about 2,000 andmore preferably from about 200 to 800. Examples of preferred radiationcurable materials include polyethylene glycol-300 diacrylate (averagePEO molecular weight about 300), polyethylene glycol-480 diacrylate, andthe corresponding methacrylates.

Further examples of the polymeric materials finding use within the scopeof the present invention are disclosed in U.S. Pat. No. 5,037,712, thedisclosure of which is incorporated herein by reference in its entirety.

The polymer layer in another preferred embodiment is an intrinsicallyconducting polymer, in the sense that it is substantially composed of anetwork of conjugated double bonds. Such conducting polymers aretypically used in doped form. U.S. Pat. Nos. 4,222,903 and 4,204,216 aredirected to the manufacture and doping of polyacetylene, a preferredexample of this class of polymer finding use in this invention. Thedisclosures of the latter and former patent are incorporated herein byreference in their entireties. Other conducting polymers which may beused include polypyrrol, polyaniline, polyazine, poly(paraphenylene),poly(thiophene), and poly(phenylene vinylene). The intrinsicallyconducting polymers may be thermosetting and can be cast from the melt.If soluble in a suitable solvent, such as anhydrous tetrahydrofuran, theconducting polymer can be coated on a substrate as the solute in such asolution and the volatile solvent removed.

The cathode is typically comprised of a compatible cathodic material(for example, insertion compounds) which is any material which functionsas a positive pole in a solid electrolytic cell. Such compatiblecathodic materials are well known in the art and include, by way ofexample, manganese oxides, molybdenum oxides, vanadium oxides, V₆ O₁₃,sulfides of titanium and niobium, chromium oxide, copper oxide,lithiated manganese oxides, lithiated cobalt oxides and the like. Theparticular compatible cathodic material employed is not critical.

In one preferred embodiment, the compatible cathodic material is mixedwith an electroconductive material including, by way of example,graphite, powdered carbon, powdered nickel, metal particles, conductivepolymers (i.e., characterized by a conjugated network of double bondslike polypyrrol and polyacetylene), and the like, and a binder such aspoly(tetrafluoroethylene) to form under pressure a positive cathodicplate.

In another preferred embodiment, the cathode is prepared from a cathodepaste which comprises from about 35 to 65 weight percent of a compatiblecathodic material; from about 1 to 20 weight percent of anelectroconductive agent; from about 0 to 20 weight percent ofpolyethylene oxide having a number average molecular weight of at least100,000; from about 10 to 50 weight percent of solvent comprising a 10:1to 1:10 mixture of an organic carbonate and a glyme; and from at leastabout 5 weight percent to about 30 weight percent of a solid matrixforming monomer or partial polymer thereof. (All weight percents arebased on the total weight of the cathode.)

The cathode paste is typically spread onto a suitable support such as acurrent collector and then cured by conventional methods to provide fora solid positive cathodic plate. The cathode (excluding the support)generally has a thickness of about 20 to about 150 microns.

Methodology

To produce the inventive lithium or lithium alloy metal polymercomposite, the solid lithium or lithium alloy metal powders and thepolymer materials are mixed together. The polymer materials may beeither a polymer precursor composition, or a solution containing apolymer solute or a polymer liquid melt. In the case where the polymermaterial is a radiation curable polymerizable, or cross linkable,polymer precursor, the mixture is passed through a source of actinicradiation. Similarly, if the polymer material is a thermally curablepolymer precursor, the mixture is heated to initiate polymerization. Ineach case, suitable catalysts known to the art, may be present in themixture to initiate/accelerate the process. As is also known to the art,surfactants may be present in minimal amounts.

The polymer materials are coated on the lithium or lithium alloy metalsurface by means heretofore described and well known in the art. If aradiation curable polymer material is used, the curable coating isexposed to a source of actinic radiation to cure the polymer layer onthe metal surface. The term "actinic radiation" includes the entireelectromagnetic spectrum, electron beam and gamma radiation. However,because of availability, simplicity and the reactions involved, electronbeam and ultraviolet sources will be used. The beam dosage orultraviolet intensity are adjusted to control the degree of crosslinking in a known manner.

The method of the present invention can also be used to produced a freestanding polymer film, wherein the mixture is poured into a mold orcoated onto a surface having a release characteristic such aspolytetrafluoroethylene. The cured film can be assembled between theanode and the solid electrolyte.

The solid, solvent-containing electrolyte is preferably prepared bycombining a solid matrix forming monomer with an inorganic ion salt anda solvent mixture of an organic carbonate and a glyme. The resultingcomposition is then uniformly coated onto a suitable substrate (e.g.,aluminum foil, a glass plate, a lithium anode, a cathode, etc.) by meansof a roller, a doctor blade, a bar coater, a silk screen or spinner toobtain a film of this composition or its solution. In some cases, it maybe necessary to heat the composition so as to provide for a coatablematerial.

Preferably, the amount of material coated onto the substrate is anamount sufficient so that after curing, the resulting solid,solvent-containing electrolyte has a thickness of no more than about 250microns (μm). Preferably, the solid, solvent-containing electrolyte hasa thickness of from about 10 to about 250 microns, more preferably fromabout 20 to about 150 microns.

The electrolyte composition typically comprises from about 5 to about 25weight percent of an inorganic ion salt based on the total weight of theelectrolyte; preferably, from about 8 to 20 weight percent.

The electrolyte composition typically comprises from about 40 to about80 weight percent solvent based on the total weight of the electrolyte;preferably from about 60 to about 80 weight percent; and even morepreferably about 70 weight percent.

The solid electrolyte composition typically comprises from about 5 toabout 30 weight percent of the solid polymeric matrix based on the totalweight of the electrolyte; preferably from about 10-12 to about 20-25weight percent; and even more preferably about 17-20 weight percent.

In a preferred embodiment, the electrolyte composition further comprisesa small amount of a film forming agent. Suitable film forming agents arewell known in the art and include, by way of example, polyethyleneoxide, polypropylene oxide, copolymers thereof, and the like, having anumbered average molecular weight of at least about 100,000. Preferably,the film forming agent is employed in an amount of about 1 to about 10weight percent and more preferably at about 2.5-3.5 weight percent basedon the total weight of the electrolyte composition.

The composition is cured by conventional methods to form a solid film.For example, when the solid matrix forming monomer contains a reactivedouble bond, suitable curing methods include heating, irradiation withUV radiation, irradiation with electron beams (EB), etc. When thecomposition is cured by heating or UV radiation, the compositionpreferably contains an initiator. For example, when curing is byheating, the initiator is typically a peroxide such as benzoyl peroxide,methyl ethyl ketone peroxide, t-butyl peroxypyvarate, diisopropylperoxycarbonate, and the like). When curing is by UV radiation, theinitiator is typically benzophenone, Darocur® 1173 (Ciba Geigy, Ardlesy,N.Y.), and the like.

The initiator is generally employed in an amount sufficient to initiatethe polymerization reaction. Preferably, the initiator is employed at upto about 1 weight percent based on the weight of the solid matrixforming monomer.

When curing is by EB treatment, an initiator is not required.

In an alternative embodiment, the solid polymeric matrix (e.g., formedby polymerization of a solid matrix forming monomer) can be dissolvedinto a suitable volatile solvent and the requisite amounts of theinorganic ion salt and solvent mixture of an organic carbonate and aglyme are then added. The mixture is then applied onto a suitablesubstrate (e.g., the surface of the cathode opposite to the currentcollector) in the manner set forth above and the volatile solventremoved by conventional techniques to provide for a solid electrolyte.Suitable volatile solvents preferably have a boiling point of less than85° C. and more preferably between about 45° and 85° C. Particularlypreferred volatile solvents are aprotic solvents. Examples of suitablevolatile solvents include acetonitrile, anydrous tetrahydrofuran, andthe like. However, acetonitrile is not preferred if it is to contact theanode.

In either case, the resulting solid electrolyte is a homogeneous, singlephase material which is maintained upon curing, and does not readilyseparate upon cooling to temperatures below room temperature. See, forexample, U.S. Pat. No. 4,925,751 which is incorporated herein byreference in its entirety.

Additionally, it is desirable to avoid the use of any protic materialswhich will be incorporated into the battery. For example, most of theprotic inhibitors in di- and triacrylate monomers as well as in theurethane acrylate prepolymers are preferably removed prior to formationof the cathode and/or electrolyte. In this regard, removal of theseinhibitors down to a level of less than 50 parts per million (ppm) canbe accomplished by contacting these monomers and prepolymers with aninhibitor remover. Suitable inhibitor removers are commerciallyavailable.

In a preferred embodiment, the process of forming an electrolytic cellcomprises the steps of coating the surface of a cured or uncured cathodewith a composition comprising a solid matrix forming monomer, aninorganic ion salt and the solvent mixture of an organic carbonate and atriglyme compound. The composition is then cured to provide for a solidelectrolyte on the cathodic surface. The anode (e.g., a lithium foil) isthen laminated to this composite product in such a way that the solidelectrolyte is interposed between the lithium foil and the cathodicmaterial.

This process can be reversed so that the surface of a anode is coatedwith a composition comprising a solid matrix forming monomer, aninorganic ion salt and the solvent mixture of an organic carbonate and aglyme compound. The composition is then cured to provide for a solidelectrolyte on the anodic surface. The cathode is then laminated to thiscomposite product in such a way that the solid electrolyte is interposedbetween the lithium foil and the cathodic material.

Methods for preparing solid electrolytes and electrolytic cells are alsoset forth in U.S. Pat. Nos. 4,830,939 and 4,925,751 which areincorporated herein by reference in their entirety.

EXAMPLE

A solid electrolytic cell is prepared by first preparing a cathodicpaste which is spread onto a current collector and is then cured toprovide for the cathode. An electrolyte solution is then placed onto thecathode surface and is cured to provide for the solid electrolytecomposition. Then, the anode is laminated onto the solid electrolytecomposition to provide for a solid electrolytic cell. The specifics ofthis construction are as follows:

A. The Current Collector

The current collector employed is a sheet of aluminum foil having alayer of adhesion promoter attached to the surface of the foil whichwill contact the cathode so as to form a composite having a sheet ofaluminum foil, a cathode and a layer of adhesion promoter interposedtherebetween.

Specifically, the adhesion promoter layer is prepared as a dispersedcolloidal solution in one of two methods. The first preparation of thiscolloidal solution for this example is as follows:

84.4 weight percent of carbon powder (Shawinigan Black™--available fromChevron Chemical Company, San Ramon, Calif.)

337.6 weight percent of a 25 weight percent solution of polyacrylic acid(a reported average molecular weight of about 90,000, commerciallyavailable from Aldrich Chemical Company--contains about 84.4 gramspolyacrylic acid and 253.2 grams water) 578.0 weight percent ofisopropanol

The carbon powder and isopropanol are combined with mixing in aconventional high shear colloid mill mixer (Ebenbach-type colloid mill)until the carbon is uniformly dispersed and the carbon particle size issmaller than 10 microns. At this point, the 25 weight percent solutionof polyacrylic acid is added to the solution and mixed for approximately15 minutes. The resulting mixture is pumped to the coating head and rollcoated with a Meyer rod onto a sheet of aluminum foil (about 9 incheswide and about 0.0005 inches thick). After application, thesolution/foil are contacted with a Mylar wipe (about 0.002 inches thickby about 2 inches and by about 9 inches wide--the entire width ofaluminum foil). The wipe is flexibly engaged with the foil (i.e., thewipe merely contacted the foil) to redistribute the solution so as toprovide for a substantially uniform coating. Evaporation of the solvents(i.e., water and isopropanol) via a conventional gas-fired oven providesfor an electrically-conducting adhesion-promoter layer of about 6microns in thickness or about 3×10⁻⁴ grams per cm². The aluminum foil isthen cut to about 8 inches wide by removing approximately 1/2 inch fromeither side by the use of a conventional slitter so as to remove anyuneven edges.

In order to further remove the protic solvent from this layer, the foilis redried. In particular, the foil is wound up and a copper supportplaced through the roll's cavity. The roll is then hung overnight fromthe support in a vacuum oven maintained at about 130° C. Afterwards, theroll is removed. In order to avoid absorption of moisture from theatmosphere, the roll is preferably stored into a desiccator or othersimilar anhydrous environment to minimize atmospheric moisture contentuntil the cathode paste is ready for application onto this roll.

The second preparation of this colloidal solution comprises mixing 25lbs of carbon powder (Shawinigan Black™--available from Chevron ChemicalCompany, San Ramon, Calif.) with 100 lbs of a 25 weight percent solutionof polyacrylic acid (average molecular weight of about 240,000,commercially available from BF Goodrich, Cleveland, Ohio, as Good-RiteK702--contains about 25 lbs polyacrylic acid and 75 lbs water) and with18.5 lbs of isopropanol. Stirring is done in a 30 gallon polyethylenedrum with a gear-motor mixer (e.g., Lightin Labmaster Mixer, modelXJ-43, available from. Cole-Parmer Instruments Co., Niles, Ill.) at 720rpm with two 5 inch diameter A310-type propellers mounted on a singleshaft. This wets down the carbon and eliminates any further dustproblem. The resulting weight of the mixture is 143.5 lbs and containssome "lumps".

The mixture is then further mixed with an ink mill which consists ofthree steel rollers almost in contact with each other, turning at 275,300, and 325 rpms respectively. This high shear operation allowsparticles that are sufficiently small to pass directly through therollers. Those that do not pass through the rollers continue to mix inthe ink mill until they are small enough to pass through these rollers.When the mixing is complete, the carbon powder is completely dispersed.A Hegman fineness of grind gauge (available from Paul N. Gardner Co.,Pompano Beach, Fla.) indicates that the particles are 4-6 μm with theoccasional 12.5 μm particles. The mixture can be stored for well over 1month without the carbon settling out or reagglomerating.

When this composition is to be used to coat the current collector, anadditional 55.5 lbs of isopropanol is mixed into the composition workingwith 5 gallon batches in a plastic pail using an air powered shaft mixer(Dayton model 42231 available from Granger Supply Co., San Jose, Calif.)with a 4 inch diameter Jiffy-Mixer brand impeller (such as an impelleravailable as Catalog No. G-04541-20 from Cole Parmer Instrument Co.,Niles, Ill.). Then, it is gear pumped through a 25 μm cloth filter(e.g., So-Clean Filter Systems, American Felt and Filter Company,Newburgh, N.Y.) and Meyer-rod coated as described above.

B. The Cathode

The cathode is prepared from a cathodic paste which, in turn, isprepared from a cathode powder as follows:

i. Cathode Powder

The cathode powder is prepared by combining 90.44 weight percent V₆ O₁₃[prepared by heating ammonium metavanadate (NH₄ ⁺ VO₃ ⁻) at 450° C. for16 hours under N₂ flow] and 9.56 weight percent of carbon (from ChevronChemical Company, San Ramon, Calif. under the tradename of ShawiniganBlacks™). About 100 grams of the resulting mixture is placed into agrinding machine (Attritor Model S-1 purchased from Union Process,Akron, Ohio) and ground for 30 minutes. Afterwards, the resultingmixture is dried at about 260° C. for 21 hours.

ii. Cathode Paste

A cathode paste is prepared by combining sufficient cathode powder toprovide for a final product having 45 weight percent V₆ O₁₃.

Specifically, 171.6 grams of a 4:1 weight ratio of propylenecarbonate:triglyme is combined with 42.9 grams of polyethylene glycoldiacrylate (molecular weight about 400 available as SR-344 from SartomerCompany, Inc., Exton, Pa.), and about 7.6 grams of ethoxylatedtrimethylolpropane triacylate (TMPEOTA) (molecular weight about 450available as SR-454 from Sartomer Company, Inc., Exton, Pa.) in a doubleplanetary mixer (Ross #2 mixer available from Charles Ross & Sons,Company, Hauppag, N.Y.).

A propeller mixture is inserted into the double planetary mixer and theresulting mixture is stirred at a 150 rpms until homogeneous. Theresulting solution is then passed through sodiated 4A molecular sieves.The solution is then returned to double planetary mixer equipped withthe propeller mixer and about 5 grams of polyethylene oxide (numberaverage molecular weight about 600,000 available as Polyox WSR-205 fromUnion Carbide Chemicals and Plastics, Danbury, Conn.) is added to thesolution vortex from by the propeller by a mini-sieve such as a 25 meshmini-sieve commercially available as Order No. 57333-965 from VWRScientific, San Francisco, Calif.

The solution is then heated while stirring until the temperature of thesolution reaches 65° C. At this point, stirring is continued until thesolution is completely clear. The propeller blade is removed and thecarbon powder prepared as above is then is added as well as anadditional 28.71 grams of unground carbon (from Chevron ChemicalCompany, San Ramon, Calif. under the tradename of Shawinigan Blacks™).The resulting mixture is mixed at a rate of 7.5 cycles per second for 30minutes in the double planetary mixer. During this mixing thetemperature is slowly increased to a maximum of 73° C. At this point,the mixing is reduced to 1 cycle per second the mixture slowly cooled to40° C. to 48° C. (e.g. about 45° C.). The-resulting cathode paste ismaintained at this temperature until just prior to application onto thecurrent collector.

The resulting cathode paste has the following approximate weight percentof components:

    ______________________________________                                        V.sub.6 O.sub.13     45    weight percent                                     Carbon               10    weight percent                                     4:1 propylene carbonate/tri-                                                                       34    weight percent                                     glyme                                                                         polyethylene oxide   1     weight percent                                     polyethylene glycol  8.5   weight percent                                     diacrylate                                                                    ethoxylated trimethylol-                                                                           1.5   weight percent                                     propane triacrylate                                                           ______________________________________                                    

In an alternative embodiment, the requisite amounts of all of the solidcomponents are added to directly to combined liquid components. In thisregard, mixing speeds can be adjusted to account for the amount of thematerial mixed and size of vessel used to prepare the cathode paste.Such adjustments are well known to the skilled artisan.

In order to enhance the coatability of the carbon paste onto the currentcollector, it may be desirable to heat the paste to a temperature offrom about 60° C. to about 130° C. and more preferably, from about 80°C. to about 90° C. and for a period of time of from about 0.1 to about 2hours, more preferably, from about 0.1 to 1 hour and even morepreferably from about 0.2 to 1 hour. A particularly preferredcombination is to heat the paste at from about 80° C. to about 90° C.for about 0.33 to about 0.5 hours.

During this heating step, there is no need to stir or mix the pastealthough such stirring or mixing may be conducted during this step.However, the only requirement is that the composition be heated duringthis period. In this regard, the composition to be heated has a volumeto surface area ratio such that the entire mass is heated during theheating step.

A further description of this heating step is set forth in U.S. patentapplication Ser. No. 07/968,203 filed Oct. 29, 1992 as Attorney DocketNo. 1116 and entitled "METHODS FOR ENHANCING THE COATABILITY OF CARBONPASTES TO SUBSTRATES", which application is incorporated herein byreference in its entirety.

The so-prepared cathode paste is then placed onto the adhesion layer ofthe current collector described above by extrusion at a temperature offrom about 45° to about 48° C. A Mylar cover sheet is then placed overthe paste and the paste is spread to thickness of about 90 microns (μm)with a conventional plate and roller system and is cured by continuouslypassing the sheet through an electron beam apparatus (Electro-curtain,Energy Science Inc., Woburn, Mass.) at a voltage of about 175 kV and acurrent of about 1.0 mA and at a rate of about 1 cm/sec. After curing,the Mylar sheet is removed to provide for a solid cathode laminated tothe aluminum current collector described above.

C. Electrolyte

56.51 grams of propylene carbonate, 14.13 grams of triglyme, and 17.56grams of urethane acrylate (Photomer 6140, available from Henkel Corp.,Coating and Chemical Division, Ambler, Pa.) are combined at roomtemperature until homogeneous. The resulting solution is passed througha column of 4A sodiated molecular sieves to remove water and then mixedat room temperature until homogeneous.

At this point, 2.57 grams of polyethylene oxide film forming agenthaving a number average molecular weight of about 600,000 (available asPolyox WSR-205 from Union Carbide Chemicals and Plastics, Danbury,Conn.) is added to the solution and then dispersed while stirring with amagnetic stirrer over a period of about 120 minutes. After dispersion,the solution is heated to between 60° C. and 65° C. with stirring untilthe film forming agent dissolved. The solution is cooled to atemperature of between 45° and 48° C., a thermocouple is placed at theedge of the vortex created by the magnetic stirrer to monitor solutiontemperature, and then 9.24 grams of LiPF₆ is added to the solution overa 120 minute period while thoroughly mixing to ensure a substantiallyuniform temperature profile throughout the solution. Cooling is appliedas necessary to maintain the temperature of the solution between 45° and48° C.

In one embodiment, the polyethylene oxide film forming agent is added tothe solution via a mini-sieve such as a 25 mesh mini-sieve commerciallyavailable as Order No. 57333-965 from VWR Scientific, San Francisco,Calif.

The resulting solution contains the following:

    ______________________________________                                        Component         Amount        Weight Percent.sup.a                          ______________________________________                                        Propylene Carbonate                                                                             56.51  g      56.51                                         Triglyme          14.13  g      14.13                                         Urethane Acrylate 17.56  g      17.56                                         LiPF.sub.6        9.24   g      9.24                                          PEO Film Forming Agent                                                                          2.57   g      2.57                                          Total             100    g      100                                           ______________________________________                                         .sup.a = weight percent based on the total weight of the electrolyte          solution (100 g)                                                         

This solution is then degassed to provide for an electrolyte solutionwherein little, if any, of the LiPF₆ salt decomposes.

Optionally, solutions produced as above and which contains theprepolymer, the polyalkylene oxide film forming agent, the electrolytesolvent and the LiPF₆ salt are filtered to remove any solid particles orgels remaining in the solution. One suitable filter device is a sinteredstainless steel screen having a pore size between 1 and 50 μm at 100%efficiency.

Alternatively, the electrolyte solution can be prepared in the followingmanner. Specifically, in this example, the mixing procedure is conductedusing the following weight percent of components:

    ______________________________________                                        Propylene Carbonate                                                                              52.472  weight percent                                     Triglyme           13.099  weight percent                                     Urethane Acrylate.sup.b                                                                          20.379  weight percent                                     LiPF.sub.6         10.720  weight percent                                     PEO Film Forming Agent.sup.c                                                                     3.340   weight percent                                     ______________________________________                                         .sup.b (Photomer 6140, available from Henkel Corp., Coating and Chemical      Division, Ambler, PA)                                                         .sup.c Polyethylene oxide film forming agent having a number average          molecular weight of about 600,000 (available as Polyox WSR205 from Union      Carbide Chemicals and Plastics, Danbury, CT)                             

The mixing procedure employs the following steps:

1. Check the moisture level of the urethane acrylate. If the moisturelevel is less than 100 ppm water, proceed to step 2. If not, then firstdissolve the urethane acrylate at room temperature, <30° C., in thepropylene carbonate and triglyme and dry the solution over sodiated 4Amolecular sieves (Grade 514, 8-12 Mesh from Schoofs Inc., Moraga,Calif.) and then proceed to step 4.

2. Dry the propylene carbonate and triglyme over sodiated 4A molecularsieves (Grade 514, 8-12 Mesh from Schoofs Inc., Moraga, Calif.).

3. At room temperature, <30° C., add the urethane acrylate to thesolvent prepared in step 2. Stir at 300 rpm until the resin iscompletely dissolved. The solution should be clear and colorless.

4. Dry and then sift the polyethylene oxide film forming agent through a25 mesh mini-sieve commercially available as Order No. 57333-965 fromVWR Scientific, San Francisco, Calif. While stirring at 300 rpm, add thedried and pre-sifted polyethylene oxide film forming agent slowing tothe solution. The polyethylene oxide film forming agent should be siftedinto the center of the vortex formed by the stirring means over a 30minute period. Addition of the polyethylene oxide film forming agentshould be dispersive and, during addition, the temperature should bemaintained at room temperature (<30° C.).

5. After final addition of the polyethylene oxide film forming agent,stir an additional 30 minutes to ensure that the film forming agent issubstantially dispersed.

6. Heat the mixture to 68° C. to 75° C. and stir until the film formingagent has melted and the solution has become transparent to light yellowin color. Optionally, in this step, the mixture is heated to 65° C. to68° C.

7. Cool the solution produced in step 6 and when the temperature of thesolution reaches 40° C., add the LiPF₆ salt very slowly making sure thatthe maximum temperature does not exceed 55° C.

8. After the final addition of the LiPF₆ salt, stir for an additional 30minutes, degas, and let sit overnight and cool.

9. Filter the solution through a sintered stainless steel screen havinga pore size between 1 and 50 μm at 100% efficiency.

At all times, the temperature of the solution should be monitored with athermocouple which should be placed in the vortex formed by the mixer.

Afterwards, the electrolyte mixture is then coated by a conventionalknife blade to a thickness of about 50 μm onto the surface of thecathode sheet prepared as above (on the side opposite that of thecurrent collector) but without the Mylar covering. The electrolyte isthen cured by continuously passing the sheet through an electron beamapparatus (Electrocurtain, Energy Science Inc., Woburn, Mass.) at avoltage of about 175 kV and a current of about 1.0 mA and at a conveyorspeed setting of 50 which provides for a conveyor speed of about 1cm/sec. After curing, a composite is recovered which contained a solidelectrolyte laminated to a solid cathode.

D. Anode

The anode comprises a sheet of lithium foil (about 76 μm thick) which iscommercially available from FMC Corporation Lithium Division, BessemerCity, N.C. The surface of the lithium foil is coated as heretoforedescribed.

E. The Solid Electrolytic Cell

A sheet comprising a solid battery is prepared by laminating the lithiumfoil anode to the surface of the electrolyte in the sheet produced instep C above. Lamination is accomplished by minimal pressure.

While the invention has been described in terms of various preferredembodiments, the skilled artisan will appreciate the variousmodifications, substitutions, omissions and changes which may be madewithout departing from the spirit thereof. The descriptions of subjectmatter in this disclosure are illustrative of the invention and are notintended to be construed as limitations upon the scope of the invention.

What is claimed is:
 1. A coated lithium anode in an electrochemical cell that comprises a sheet of lithium or lithium alloy; wherein a surface of said sheet is coated with a layer of an electrically conducting polymer composition comprising lithium or lithium alloy particles that are dispersed in a polymer, wherein the particles comprise more than 1 weight percent of the electrically conducting polymer composition and wherein the layer of electrically conducting polymer composition is not more than about 50 microns thick.
 2. A coated lithium anode according to claim 1 wherein said particles are lithium alloy metal particles that comprise lithium and a metal selected from the group consisting of aluminum, mercury, zinc, and mixtures thereof.
 3. A coated lithium anode according to claim 1 wherein the polymer in said polymer composition comprises radiation polymerizable polyethylenically unsaturated compounds.
 4. A coated lithium anode according to claim 1 wherein said polymer composition comprises polymers which are electrically conducting polymers.
 5. A coated lithium anode according to claim 3 wherein said radiation polymerizable polyethylenically unsaturated compounds are obtained by reacting a polyethylene glycol with a polymer selected from the group consisting of acrylic acid, methacrylic acid, vinylsulfonate polyalkylene oxides, polyester acrylates, and acrylated polyurethane.
 6. A coated lithium anode according to claim 4 wherein said electrically conducting polymer is selected from the group consisting of polyacetylene, polyaniline, polyazine, poly(paraphenylene), poly(thiophene), and poly(phenylene vinylene).
 7. A coated lithium anode according to claim 1 wherein said coating forms a layer of from about 5 to about 25 microns in thickness.
 8. A coated lithium anode according to claim 1 wherein said particles have diameters from about 0.2 microns to about 4 microns.
 9. A coated lithium anode comprising a sheet of lithium or lithium alloy that is coated with a layer of a curable polymer precursor composition comprising lithium or lithium alloy metal particles that are dispersed in a curable polymer precursor, wherein the particles comprise more than 1 weight percent of the curable polymer composition and wherein the layer of curable polymer composition is not more than about 50 microns thick.
 10. A coated lithium anode according to claim 9 wherein said composition comprises polymer precursors that are selected from the group consisting of acrylates and vinyl compounds.
 11. A coated lithium anode according to claim 1 wherein the particles comprise about 20 to 40 weight percent of the electrically conducting polymer composition.
 12. A coated lithium anode comprising a sheet of lithium or lithium alloy, suitable for use as an anode in an electrochemical cell, that is fabricated by a process comprising the steps of:dispersing particles of lithium or lithium alloy metal in a polymer precursor composition; coating a surface of a sheet of lithium or lithium alloy with said polymer precursor composition; and partially or totally curing said polymer precursor composition to form an electrically conducting polymer layer that is not more than 50 microns thick and wherein said particles comprise more than 1 weight percent of electrically conductive polymer.
 13. A coated lithium anode according to claim 12 wherein said curing is carried out by exposing said polymer precursor composition to ultraviolet light or an electron beam.
 14. A coated lithium anode according to claim 12 (wherein said particles are lithium alloy metal particles that comprise lithium and a metal selected from the group consisting of aluminum, mercury zinc and mixtures thereof.
 15. A coated lithium anode according to claim 12 wherein said polymer precursor composition comprises radiation polymerizable polyethylenically unsaturated compounds.
 16. A coated lithium anode according to claim 15 wherein said radiation polymerizable polyethylenically unsaturated compounds are obtained by reacting a polyethylene glycol with a polymer selected from the group consisting of acrylic acid, methacrylic acid, vinylsulfonate polyalkylene oxides, polyester acrylates, and acrylated polyurethane.
 17. A coated lithium anode according to claim 12 wherein said particles comprise about 20 to 40 weight percent of the electrically conductive polymer.
 18. A coated lithium anode, suitable for use in an electrochemical cell, that is fabricated by a process comprising the steps of:dispersing particles of lithium or lithium alloy metal in a melt or solution of electrically conductive polymer to form a coating composition; coating a surface of a sheet of lithium or lithium alloy with said composition; and permitting said composition to form a solid polymeric layer on said surface wherein said particles comprise more than 1 weight percent of said solid polymeric layer and wherein the layer is not more than about 50 microns thick.
 19. A coated lithium anode according to claim 18 wherein said particles are lithium alloy metal particles that comprise lithium and a metal selected from the group consisting of aluminum, mercury zinc and mixtures thereof.
 20. A coated lithium anode according to claim 18 wherein said electrically conductive polymer is selected from the group consisting of polyacetylene, polyaniline, polyazine, poly(paraphenylene), poly(thiophene), and poly(phenylene vinylene).
 21. A coated lithium anode according to claim 18 wherein said solid polymeric layer is about 5 to about 25 microns in thickness.
 22. A coated lithium anode according to claim 19 wherein said particles have diameters from about 0.2 microns to about 4 microns.
 23. A coated lithium anode according to claim 18 wherein said particles comprise about 20 to 40 weight percent of said solid polymeric layer. 